Note 9 - Retirement Savings Plan (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%		100.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	4.00%		4.00%
Defined Contribution Plan, Employer Contribution Amount	$ 11,907	$ 9,770

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration